Various means have been used in the prior art to readjust the pulse forming network (PFN) voltage of a laser power supply (P/S) in a tank laser range finder system, whenever it became necessary to replace the receiver/transmitter unit (R/T) or the electronics unit (E/U) in order to insure a particular output energy. One of the problems in the past occurred when the PFN voltage of a new laser power supply was inadvertently adjusted too high and the laser fired. Under these conditions the increased energy to the laser often caused serious damage to the tank range finder optics. Additional problems relating to laser equipment are frequently encountered because of the wide variations found in laser efficiency due to differences in flash lamps, laser rod characteristics and varying optical losses. Thus in order to insure a particular output energy in prior art devices, the input energy had to be individually adjusted for each laser. Since the input energy stored in a PFN is generally given by the equation E=CV.sup.2 /2, and since the PFN capacitance, C, is usually kept constant for a given power supply unit, the PFN voltage, V, is therefore the only parameter which may be easily adjusted to vary the laser energy output. In the past the PFN voltage of a system was normally set by adjusting a variable potentiometer control element on the PFN power supply. However, one of the problems with prior art PFN voltage power supplies has been that there was no easy method of determining in advance exactly where the potentiometer should be set after either a receiver/transmitter unit or electronic unit had been replaced. The aforementioned problems are particularly critical in laser power supplies which utilize thermistor control elements for compensating for a change in laser efficiency as a function of varying ambient temperatures.
The problem of using an instrument such as an optical power meter to determine whether a PFN voltage setting is correct is that some laser firing devices, such as those used in armored vehicles, have protective ballistic covers thereon which preclude the easy attachment of an optical test set. The problem with the prior art method of first adjusting the PFN voltage potentiometer to its lowest setting and then turning the potentiometer setting higher, while firing the laser until the malfunction indication of low energy condition is extinguished, and then further adjusting the potentiometer upwards a particular number of turns, is that there is susbstantial variation in the linearity of potentiometers and of such magnitude to make the malfunction indicating points very uncertain. The prior art method for proper adjustment of PFN voltage for a tank laser range finder system generally necessitated removal of both the electronic unit and the receiver/transmitter unit regardless of which needed repair. The repaired system was then connected to a test set and adjusted for proper laser energy output. This aforedescribed method was both time consuming and laborius.